Seating units that are convertible into beds are popular with consumers because of their multifunctionality. Many consumers find it very convenient to have a sofa or chair that can provide a bed for a guest, as such a unit can eliminate the need for an additional, separate bed. One popular sofa-bed design includes its own complete mattress that is folded within the cavity of the sofa during periods of non-use. One such example is illustrated in U.S. Pat. No. 4,200,941 to Gill et al. This type of sofa-bed can be quite heavy, and typically requires not only the separate mattress, but also a relatively intricate mechanism to control the unfolding and folding of the mattress.
Other sofa-beds lack a complete mattress, but instead are constructed of separate sections that serve as support surfaces of the sofa and unfold to form a flat, mattress-like sleeping surface. An example of a convertible sofa of this type is illustrated in U.S. Pat. No. 4,737,996 to Tiffany (Tiffany). The Tiffany sofa-bed includes a backrest, a seat and a “subseat” that unfold to form the horizontal sleeping surface. In the folded “sofa” configuration, the backrest is generally upright, and the seat and “subseat” fold upon each other (with the subseat in an inverted position). The backrest is guided between positions by preformed slots in the arms of the sofa that receive posts that extend laterally from the backrest. The backrest is coupled to the seat and subseat via an angled link. The subseat is pivotally attached at one end to the arms and is hinged at the other end to the seat. This arrangement is described in Tiffany as being particularly economical and having relatively few moving parts.
Although the Tiffany-style sofa-bed has been popular with some consumers, it may be desirable to provide a sofa-bed that is less expensive and/or easier to manufacture, as the formation of the slots to guide the backrest can be expensive.